Recovery of light oils



Filed Feb. 18. 1930 3 Sheets-Sheat 1 |NvEN'roR 5 52m 72M MM r MArroRNEYs June 28, 1932. s. P. MILLER ETAL RECOVERY 0F LIGHT OILS .FiledFeb. 18. 1930 3 Sheets-Sheet 2 kuwitSJ ATTORN EYS June '28, 1932. s. P.MILLER ET AL.

RECOVERY 0F LIGHT OILS y 3 sheets-'sheet s Filed Feb. 18. 1930 MMYSQ. I

Qmfl

ATTORN EY Patented June 28, 1932 PATENT AOFFICE STUART PARMELEE MILLER,F ENGLEWOOD, AN D EDWARD I-L ELLIS, 0F MORSENIERE,

NEW JERSEY, ASSIGNORS T0 THE BARRETT COMPANY, 0F NEW YORK, N. Y., A.COB- POBATION OF NEW JERSEY RECOVERY OF LIGHT OILS Application ledFebruary 18, 1930. Serial No. 429,804.

This invention relates to the recovery o f sulting high boiling coal taroil as creosote oil, etc.

Coal distillation gases such as the gases from a coke oven plant or agas retort plant are ordinarily cooled to separate condensableconstituents and then after lpassing the gases through an ammonia absorer the gases are ordinarily Washed with a high boiling oil to remove thevapors of oils of low boiling range which, alone, are condensable, butwhich are present in the vcoal distillation gases at such dilution thatthey are not condensable from the gas mixture at temperaturespractically attainable in plant operation. The oils of low boiling rangeare known as light oil. They consist chiefly of aromatic hydrocarbonswith a boiling range from about C. to 180 C., although the boiling rangemay vary depending upon the operation of the coal distillation plant.The light oil may contain some unsaturated compounds and also paraiinhydrocarbons, depending upon the coal distilling operation.

Straw oil, a high boiling, limpid petroleum product, is often employedas a wash oil for absorbing the light oil from the coal distillationgases. After the gases leave the ammonia absorber they are passedthrough one or more absorption towers through which straw oil is allowedto trickle. The absorption towers expose a large surface of the wash oilto the ases, and the li ht oil present in the gases 1s absorbed by t eoil. The operation is a countercurrent operation so that the fresh oilis brought into direct contact with the gases from which most of thelight oil has been absorbed. The straw oil which has been used to absorbthe light oil from the gases, which is referred to as benzolized washoil, is then heated to distill off the light oil. It is then referred toas debenzolzed wash oil. The light oil distillate may be treated for theproduction of desired light oil lconstituents, such as motor fuel,benzene, toluene, Xylenes, solvent naphtha, etc. The debenzolized strawoil is then used again for the absorption of further light oil from thegases. Instead of straw oil other oils may be employed which have asufficiently high boilin point to permit recovery of the light oil ydistillation from the wash oil.

In the past diiiiculties have arisen in operating light oil recoverysystems; owing to the fact that the wash oil removes from the gaseshigher boiling constituents such as naphthalene, coumarone, indene, etc.which are not completely volatilized at the rela.- tively lowtemperature em loyed for separating the light oil from t e wash oil, thewash oil eventually becomes contaminated with such substances and theirdecomposition and polymerization products, which result from heating thewash oil to distill off the light oil. Straw oil or other wash oil whichhas been in use for some little time becomes contaminated 'with suchforeign substances, and it is necessary to purify the wash oil atintervals. This necessitates keeping a considerable stock of the Washoil on hand, and involves distillation costs, etc. which we now find areunnecessary.

According to this invention, we employ as a wash oil a coal tardistillate of relativel high boiling range, for example 250-300 andupwards. This is employed in the way that straw oil or any other washoil would be `employed to remove light oil from the gases.

It is a more effective absorbent light oil than the absorbing oilsgenerally employed. Coal tar distillate which has been used forabsorbing light oil, generally referred to as benzolized Wash oil, i. e.benzolized distillate is then heated to distill o the light oil. Theresulting debenzolized creosote oil may then be disposed of as creosoteoil directly, or it may be employed in the preparation of coal tarsolutions directly, or b recirculating it through the light oil absoring towers it may be reused several times and then be disposed of asabove, or otherwise as a coal tar product. In any case according to minvention the necessity is eliminated of su jecting the absorbing oil topuriiication or refining to remove undesired substances absorbed orderived from the gases. Such undesired substances if accumulated instraw oil, for example, would eventually prevent further use of thestraw oil as a Wash oil unless such substances were first removed as bydistillation.

According to a preferred method of carrying out the invention, tarrecovered from the coal distillation gases or a portion of the tarrecovered from the coal distillation gases is distilled at the coaldistillation plant. The high boiling oil fraction, which may be thefraction with a boiing range from Z-300 C. and upward, for example, asit is produced, or a portion of the distillate of this boiling range,may be used directly in the light oil absorption process, and afterbeing debenzolized it may he run to storage. it may be blended withother distillate of this boiling range or distillate of another range orit may be blended with tar to produce coal tar solution. According tothis invention the debenzolized oil is sold directly as such, or it isblended as such, without being treated for the removal of naphthalene orcondensation and polymerization products, etc. which may result from thelight oil absorption and subsequent distillation to volatilize the lightoil.

The coal tar distillate under special conditions may be used as Wash oilonly once; ordinarily it will advantageously be recirculated severaltimes through the absorbing towers and then through the light oil stiilbefore being run to storage. One batch of distillate may be employed asWash oil for a Whole day, for example, before being run to storage.

When straw oil or a wash oil other than coal tar distillate is used orabsorbing light oil from coal distillation gases any distillation of theWash oil which may occur during the absorbin operation Will cause thepresence of constituents of the straw oil or other Wash oil in the coaldistillation gases as a foreign substance. Similarly, any of the strawoil or other Wash oil-which may distill over in the strip ing still inwhich the light oil is distilled rom the Wash oil will be present in thelight oil distillate as a foreign substance largely of a paraHine-likenature. When a coal tar oil is used, however, any distillate from thecoal tar oil Which goes over with the gases or with the light oil is nota foreign substance since the coal tar distillate is derived originallyfrom coal distillation gases; a purer and more valuable light oil istherefore obtained when the Wash oil is coal tar distillate.

. Further, the tendency of the coal tar distillate to distill in theabsorbing towers is negligible since the gases are already saturatedwith constituents of the coal tar distiliate. By removal of light oilfrom the gases, the volume of the gases is reduced and the amount ofhigher boiling constituents necessary to saturate the gases is likewisereduced. Instead of distilling any of the Wash oil into the gasestherefore, the tend ency is for the volume of the Wash oil to beincreased somewhat, owing to condensation of higher boiling constituentsfrom the gases. When coal tar distillate is employed as the Wash oil,such increase does not introduce foreign substances into the Wash oil.Any increase which is brought about in this manner increases the amountof coal tar distillate.

Ordinary coal distillation gases as they come from the ammonia absorberscontain line suspended particles of tar, i. e. tar fog. lVash oilemployed for scrubbing such ordinary gases removes at least a portion ofthe suspended tar particles from the gases and the tar contaminates theWash oil. There coal tar distillate is employed for Washing the gases toremove light oii, the distillate will become contaminated with traces oftar. Distillate which has been so used and Which is contaminated with asmall amount of tar may be employed directly for the preparation of coaltar solution by blending with coal tar in the proper proportions afterfirst being debenzolized.

It the coal tar distillate used for recover ing light oil from the gasesis to be disposed of as a clean oil product, for example clean creosoteoil, it may be desirable to clean the gases in an electricalprecipitator before they are scrubbed with the coal tar oil. When thelight oil absorbers are located beyond the ammonia saturator, theprecipitator may be located between the ammonia saturator and the lightoil absorber, or it may be located ahead of the ammonia saturator. Theprecipitator removes all entrained particles from the gases so that coaltar distillate used in the light oil absorbers will remain free from tarparticles, etc., and can be disposed of as a clean coal tar product.

An electrical precipitator may be located beyond the light oil absorberto remove from the gases traces of oil which may be carried from theby-product recovery system as a suspension of small drops.

The apparatus for carrying out the invention may be a byproduct recoverysystem of any usual type, including a light oil absorber and a strippingstill for removing the light oil from the wash oil employed in theabsorber.

The still employed for the distillation of tar may be any tar still, butaccording to a preferred method of carrying out the invention, a stillin which the tar is distilled by direct contact with the hot coaldistillation gases is employed.

The invention will be further described in connection with theaccompanying drawin s.

Fig. 1 is a flow sheet illustrating the app ication of the invention tola coke oven battery;

Fig. 2 is a plan view showing a coke oven battery and one type of tarstill which may be employed for distilling tar by direct contact withthe coke oven gases;

Fig. 3 is an elevation of the apparatus shown in Fig. 2; and

Fig. 4 is a section on the line 4 4 of Fig. 3.

The numbers indicated in parentheses on the flow sheet correspond withthe parts of the apparatus shown in Figs. 2 and 3.

The invention may be carried out in the usual by-product recoveryapparatus with such additional apparatus as may be necessary forproducing and handling the coal tar distillate. As indicated in Fig. 1,the coal distillation gases which in the drawings are represented as thegases from a coke oven battery are cooled to separate tar. The coolingmay be eiected in the ordinary collector main and condensers. The tardistilled may be all or a part of the total tar combined by mixing thetar from several sources, such as the collector main and condensers, orall or a part of any tar fraction may be distilled. The gases areordinarily passed through an ammonia saturator or absorber in whichWater or sulfuric acid is used for extracting the ammonia before thegases pass to a benzol extractor and the apparatus shown provides forsuch removal of ammonia.

Any tar still suitable for producing distillate of the desired highboiling range may be used. The distillate or a portion of the distillateis employed for extracting the light oil in the so-called benzolextractor. From the benzol extractor the gases pass to a storage tank orto burners. The gases may when required he treated for the removal ofsulfur compounds, etc., in the usual Way.

The Wash oil leaving the benzol extractor is commonly referred to asbenzolized Wash oil. It contains benzol and other light oil. It isintroduced into a stripping still which may be any usual type ofstripping still. Ordinarily a steam heated column still is employed inwhich live steam is also introduced to assist in volatilizing the lightoil. Heat interchangers, etc. may be employed in the usual manner torecover heat from the vapors and from the nonvolatilized wash oil, whichin this case is creosote distillate with the addition of anynaphthalene, or other high boiling impurities which are added to thedistillate during the light oil extraction. This coal tar oil may thenbe run directly to storage to be disposed of as creosote oil or to beused for blending for the production of coal tar solution, etc. It maybe blended with other coal tar distillate of high boiling range, whichhas Vnot been used as Wash oil, or

all or a part ofthe distillate may be again passed through the benzolextractor and used for the recovery of further light oil.

The wash oil from which light oil has been removed in the strippingstill is referred to as debenzolized Wash oil. Instead of passing thedebenzolized Wash oil directly to storage, all or a portion of the oilmay be recirculated as shown in dotted lines for reuse in the benzolextractor. Fresh Wash oil, i. e. fresh distillate, is added to the cycleto rgfplace any debenzolized oil which is drawn o to storage.

Figs. 2 and 3 show a preferred form of distilling apparatus. The cokeoven battery is indicated at 5. It is equipped in the usual Way with acollector main 6 which is connected with the individual ovens of thebattery through uptake pipes 7. A cross-over main 8 connects thecoilector main with condensers 9. From the condensers the gases pass tothe ammonia saturator and benzol eX- tractor or Wash oil absorber (notshown in Figs. 2 and 3). This apparatus may be of the usual type.

The tar still 10 is located on the opposite side of the coke oven blockfrom the collector main. Selected ovens of the battery are provided withuptake pipes 11. A hot gas header 12 connects these uptake pipes withthe still A10. By proper manipulation of valves in the uptake pipes 7and 11 the gases from selected ovens are passed into the still insteadof into the collector main. In the still is a roll 13 which is driven ata high speed, for example 960-1200 R. P. M., by the motor 14. Thissprays tar or pitch from the bottom of the still up into the hot cokeoven gases passing through the still in the form of a tine intense spraywhich scrubs and detars the gases. Tar is distilled to pitch which isdrawn ofi' through the coke trap 15 and the levelling arm 16. Theposition of this levelling arm determines the depth of the tar and pitchmaintained within the still and thus determines the nature of the tarspray produced by the roll 13. The pitch is drawn oil' into the trough17 Where it is chilled and granulated by a jet of cold water from thepipe 18.

The gases and vapors from the still 10 pass into the saturator 19. Taris sprayed into the saturator thru the nozzle 20. Baiiies 21 and 22 areprovided to remove particles of tar entrained in the gases and toprovide a large surface of Contact between the tar sprayed in thru thenozzle 20 and-the hot gases and vapors which pass up thru the saturator.The tar is distilled to semi-pitch in this saturator. from the bottom ofthe saturator thr';V the main 23 and introduced into the still at theend at Which the hot gases enter from the header 12. This partiallydistilled tar or semi-pitch is further distilled in the still Thesemi-pitch is drawn off 1 and a pitch of high melting point may readilybe produced.

The gases and vapors from the saturator pass into the heat interchanger25. The tar to be distilled, or a portion of this tar, is passed thruthe heat interchanger thru the coil 26 where it is preheated, and it isconveyed by the pipe 27 to the nozzle 20. The hot gases and vapors arepartially cooled in this heat interchanger and oil is condensed. Thecooling in the heat interchanger is so regulated that the oil fractionobtained and drawn otf into the tank E28 is a coal tar distillate ofhigh boiling range, for example 250-2750 C., or higher.

The partially cooled gases and vapors which leave the heat interchanger25 are further cooled in the condenser 30. This may be any suitable typeof condenser, either a direct condenser or indirect condenser.Distillate of low boiling range which is condensed in the condenser 3f)is drawn oti' into the tank 31. From this condenser the gases pass thruan exhauster 32 to storage or to burners. The storage tank may be thesame storage tank in Which the gases from the collector main 6 arestored.

All or a portion of the heavy creosote oil is drawn ofi' thru the line35 to the benzol eX- traetor employed for removing light oil from thegases which have passed thru the condensers 9. The resulting benzolizedoil passes to a stripping still Where the light oil is removed. Theresulting debenzolized oil may then be drawn oft' to storage. If only apart of the distillate condensed in the condenser 25 is employed as Washoil, the debenzolized Wash oil may be blended with the rest of thedistillate in the tank 28. A separate storage tank may be provided forthe debenzolized Wash oil, or it may be run directly to a blending tankfor blending with coal tar, etc., to produce coal tar solution, etc.

In the claims the reference to drawing otl' the debenzolized oil tostorage is to be interpreted to mean collecting the debenzolized washoil for disposal as creosote oil, for blending with other coal tardistillate to be disposed of as creosote oil, etc., or for blending withother materials to produce coal tar products, such as coal tar solution.

We claim:

1. The method of recovering light oil from coal distillation gases,which comprises cooling the coal distillation gases to separate a coaltar, distilling the coal tar so as to produce a coal tar distillate ofhigh boiling range. bringing this distillate into direct contactwith'the coal distillation gases after cooling, and after the removal ofammonia, to absorb light oil therefrom, stripping the resulting 5 oil tostorage.

2. The method of recovering light oil from coal distillation gases,which comprises cooling the coal distillation gases to separate a coaltar, distilling the coal tar so as to produce a coal tar distillate ofhigh boiling range, bringing this distillate into direct contact withthe coal distillation gases after cooling and after the removal ofammonia to absorb light oil therefrom, stripping the resulting solutionof light oil in coal tar distillate to remove light oil, reusing atleast a portion of the resulting oil for further extraction of light oiland `stripping it to remove light oil, and running the resulting oil tostorage.

3. The method of recovering light oil from coal distillation gases,which comprises bringing a high boiling coal tar distillate into directand intimate contact with the gases to absorb light oil therefrom,separating the light oil from the high boiling distillate bydistillation, and reusing at least a portion of the resulting oil forfurther extraction of light oii from coal distillation gases` andrepeating the operation and ruiming the resulting oil from which lightoil has been distilled to storage before it becomes contaminated withundesirable constituents to such an extent that it is no longer usefulfor creosoting purposes.

4. The method of recovering light oil from coal distillation gases whichhave been cleaned in an electrical precipitator, which comprisesbringing high boiling coal tar distillate into direct and intimatecontact With the gases to absorb light oil therefrom. separating thelight oil by distiliation and reusing at least a portion of theresulting oil for turther extraction of light oil from coal distillationgases, and repeatingthe operation and running the oil from which lightoil has been distilled to storage before it becomes conta minated withundesirable constituents to such an extent that it is no longer usefulas coal tar distiilate.

5. The method of recovering light oil from coal distillation gases.`which comprises bringing cooled coal distillation gases into directcontact with high boiling coal tar distillate so as to dissolve lightoil therein. heating the distillate to distill off the light oil.reusing at least a portion of the resulting oil for further extractionof light oil from the gases, and, finally, after removing light oil tromthe distillate, blending the resulting debenzolized oil with tar toproduce coal tar solution.

6. The method of recovering light oil from coal distillation gases,Which comprises continuously circulating coal tar distillate through abenzol extractor to bring the distillate into direct contact with thecoal distillation gases and absorb light oil from these gases and thusproduce a benzolized oil, continuously heating the benzolized oil todistill off the light oil and produce a debenzolized oil, continuallydrawing ofi' a portion of the debenzolized oil to storage, adding freshcoal tar distillate to the remainder of the debenzolized oil and againcirculating it through the benzol extractor.

7. In combination with a coal- .distillation plant and by-productrecovery system, a still, means for supplying tar recovered from thecoal distillation gases to the still, a condenser for condensing from`the resulting distillate vapors a creosote oil of high boiling range,means for introducing the creosote oil as a wash oil into the benzolextractor of the byproduct recoveryT system, a stripping still connectedwith the extractor for the removal of benzol from the wash oil and meansfor running the debenzolized wash oil from the stripping still of theby-product recovery system to storage.

8. In combination with a coke oven battery, coolers, an ammoniasaturator and a benzol extractor for treating the coal distiliationgases, a still, means for passing coal distillation gases from a portionof the plant through the still, means for introducing tar recovered fromthe gases into the still and distilling it therein, a condenser for coaltar distillate of high boiling range, means for introducing thisdistillate into the benzol extractor, a stripping still, means forintroducing benzolized wash oil from the benzol extractor into thestripping still, and means `for running benzolized wash oil from thestripping still to storage.

9. In combination with a coke oven battery, coolers, an ammoniasaturator and a benzol extractor for treating the coal distillationgases, a still, means for passing coal distillation gases from a portionof the plant through the still, means for introducing tar recovered fromthe gases into the still and distilling it therein, a condenser for coaltar distillate of high boilin range, means for introducing tar recoveredrom the gases into the still, and distilling it therein, a condenser forcoal tar distillate of high boiling range, means for introducing thisdistillate into the benzol extractor, a stripping still, means forrecirculatingthe benzolized wash oil through the benzol extractor, andmeans for running debenzolized wash oil to storage.

' 10. In combination with the by-product recovery system o a coaldistillation plant comprising a benzol extractor and a strip ing still,a still for distilling tar recovered rom the coal distillation gases, acondenser for recovering coal tar distillate of high boiling range, astorage tank, means for running a portion of this coal tar distillate ofhigh boillng range to the storage tank, means for introducing thebalance into the benzol extractor, and means for introducingdebenzolized wash oil-from the stripping still into the storage tank.

11. The method of producing coal tar oil at a coal distillation plantand recovering light oil from the coal distillation gases produced atthe plant, which comprises producing from the coal distillation gases acoal tar oil fraction substantially free from lower boiling oils, usingat least a portion oflthis fraction for the recovery of light oil fromthe coal distillation gases by scrubbing the gases therewithv aftercooling them, separating light oil from the fraction by distillation andrunning the resulting oil to storage.

l2. The method of producing coal tar oil at a coal distillation plantand recovering light oil from the coal distillation gases, whichcomprises producing from the gases, pitch and coal tar oil including acoal tar oil fraction substantially free from lower boiling oils,dividing the fraction into at least two parts, using one part of thefraction for removing light oil from the gases after cooling the gases,heating the resulting solution of the light oil in the fraction todistill off light oil and adding the resulting oil to another part ofthe fraction.

13. The method of producing coal tar oils Aat a coal distillation plantand recovering li ht oil from the coal distillation gases, whichcomprises producing from the coal distillation gases pitch and coal taroil, dividing the oil into at least two parts, using one part ofthe oilfor removing light oil from the gases after cooling the gases,distilling light oil from the resulting solution of light oil in coaltar oil and adding the residual oil to another part of the oil.

14; The method of recovering light oil from coal distillation gases,which comprises dividing a stream of coal tar oil into two parts, usingone part of the oil for removing light oil from the coal distillationgases, distilling light oil from the resulting solution and adding theresidual oil to the stream.

15, The method` of recovering light oil from coal distillation gases ata coal distillation plant, which comprises producing from the coaldistillation gases a substantially clean coal tar oil substantially freefrom lower boiling oils, passing a part of the oil directly to storage,using another part of the oil for dissolving light oil from the coaldistillation gases after cooling them, distilling light oil from theresulting solution and then passing the oil remaining after suchdistillation to the same storage.

16. The method of producing coal tar oil at a coal distillation plantand recovering li ht oil from the coal distillation gases, wichcomprises producing from the coal distillation gases pitch and coal taroil, using a part of the coal tar oil for the removal of light oil fromthe gases, distilling light oil from the resulting solution and blendingthe resulting oil with other coal tar oil which has not been used inlight oil recovery.

17. The method of producing coal tar oil l at a coal distillation plantand recovering ich comprises producing from the coal distillation gasespitch and substantially clean coal tar oil, using a coal tar oilfraction substantially free from lower boiling constituents forrecovering light oil from the gases by a cyclic process in which the oilis used for extracting the light oil from the gases, light oil isdistilled from the resulting solution and the resulting residual oil isat least in part recycled for light oil extraction, adding to the cyclefresh coal tar oil produced at the plant and blending residual oil fromthe cycle with coal tar oil produced at the plant and which is not usedfor light oil extraction.

18. In combination with a coal distillation In testimony whereof Wealiix our signatures.

S. P. MILLER. EDWARD H. ELLMS.

CERTIFICATE 0F CORRECTION.

Patent No. 1,864,749. June 28, 1932.

STUART PARMELEE MILLER ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page l,line 87, before the word "light" insert the word for; and that the saidLetters Pltent should be read with this correction therein that the samemay conform to the record of the case in the Patent Office.

Signed and sealed this 27th day of September, A. D. 1932.

M. J. Moore,

(Seal) Acting Commissioner of Patents.

ich comprises producing from the coal distillation gases pitch andsubstantially clean coal tar oil, using a coal tar oil fractionsubstantially free from lower boiling constituents for recovering lightoil from the gases by a cyclic process in which the oil is used forextracting the light oil from the gases, light oil is distilled from theresulting solution and the resulting residual oil is at least in partrecycled for light oil extraction, adding to the cycle fresh coal taroil produced at the plant and blending residual oil from the cycle withcoal tar oil produced at the plant and which is not used for light oilextraction.

18. In combination with a coal distillation In testimony whereof Wealiix our signatures.

S. P. MILLER. EDWARD H. ELLMS.

CERTIFICATE 0F CORRECTION.

Patent No. 1,864,749. June 28, 1932.

STUART PARMELEE MILLER ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page l,line 87, before the word "light" insert the word for; and that the saidLetters Pltent should be read with this correction therein that the samemay conform to the record of the case in the Patent Office.

Signed and sealed this 27th day of September, A. D. 1932.

M. J. Moore,

(Seal) Acting Commissioner of Patents.

